Sheet-metal fastening



March 11, 1930. I c CANNON I 1,749,903

. SHEET METAL FASTENING Filed May 12 1928 INVENTOR.

%' ,8 Q 9 ('fidr/esj 4/1/1021 a mY @m A TTORNEYS Patented Mar. 11, 1930 CHARLES D. CANNON, F CLEVELAND, OHIO SHEET-METAL FASTENING Application filed May 12, 1928.

Where metal sheets have to be fastened, as in the construction of cabinets, cases and other sheet metal furniture, door and-window construction, and other sheet metal building elements, it has been generally customary to employ bolts and nuts. The latter are in many instances difficult to apply, and occasion time consumption entirely disproportionate to the general character of the work.

- A fastening which is effective and simple is accordingly of fundamental importance and highly desirable.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the features hereinafter fully described, and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain structures embo-dying the invention, such being illustrative however of but a few of the various ways in which the principle of the invention may be employed. In saidannex'ed drawing Figs. 1 and 2 are sectional views, on enlarged scale, showing embodiments of the invention; Fig. 3 is a fragmentary plan view of a metal sheet as indicated in Fig. 2; Fig. 4 is a perspective view of a punching die such as may be employed in the initial shaping of the sheet as in Fig. 3; Fig. 5 is a sectional view of the punching die; Fig. 6 is a similar sectional view of a punching die of a form which may be employed for the initial shaping of a sheet as in Fig. 1; and Figs. 7, 8 and 9 are elevational views of screw threaded elements.

Referring more particularly to the drawing, there is shown in Fig. 1 a metal sheet 2 which is to be fastened with another sheet or plate element 3, a screw threaded element 4 passing through a hole in the latter, and thence engaging the sheet 2. It will be ob served that the sheet metal edge seats between the threads of the screw threaded element 4, thereby allowing of a tight draw-up and effective hold for the assemblage. The initial opening for the reception of the threaded element may advantageously be made by a punch, and for this a tool as shown in Fig. 6 may be employed, it comprising a compound punch having an outer member 5 and an inserial No. 277,234.

-- to secure an accurate placement of the edges of the sheet where encountering the screw threads, I may employ a tool having a fuller facing,'as in Figs. 4 and 5. In this, the die member 11 is more extensively recessed about the central opening, and preferably provided with an. insert member 12 which is fastened to cooperate with the outer punch member 5' and receive the inner punch member 6 in its central openlng 13. As will be noted, a sheet 2 subjected to this tool will have a hole cut cleanly therethrough, and by virture of the more exaggerated offset shoulder 14 on the punch cooperative with the shoulder 15 on the die, the radial slot 16 formed in the plate and the depressed edge will be somewhat more pronounced than in the use of the die 7, and most ofthe edge about the hole will be more markedly depressed, and yet he in parallelism to the general plane of the sheet, as shown more clearly in Fig. 2.

The screw threaded element employed has its threads spaced such as to receive between its convolutions the edges of the metal sheet to be held, and by laying out the threads in accordance with the standard gauge for sheet iron and steel, screw threaded elements are had. directly adaptable to the respective thicknesses of sheet stock customarily employed in this class of work. For example, for holding sheets of 14 gauge stock sheet steel, the

threads of the screw threaded element will be spaced correspondingly, and likewise in the case of 18 gauge, or other of the usual stocks employed. Again, in some cases thin sheets to be directly fastened in opposed relation may both seat between adjacent convolutions of appropriately spaced threads, the threads thus grip ing the edges of the two sheets. All toget ega complete working range of sizes for the usual stocks encountered will fall within convenient limits for manufacture and stock-keeping. While the character of the threa'd may be of any ofthe customary types of section, referably a square cut thread will be or inarily employed, particularly in usages involving rather heavy gauge sheet stocks. The points of the screw threaded elements may be tapered or not, as preferred in any particular instance, and the form of the head may vary, in any desired contour, slotted or lagscrew type, or round, half round as at 4:, countersink as at 4", etc.

To avoid recourse to special punching tools, a desirable type of screw threaded element may be had in accordance with this invention such as to make its own radial slot. For this, the thread is laid out to start very steeply, as illustrated in Fig. 9, the thread 17 starting almost in line with the axis of the screw, and thence gradually merging into thespacing of convolution adapted to the gauge of the sheet stock, as indicated at 17 In this manner, with a hole through the sheet at proper location, the screw threaded element may be forced thereinto, its sharpened thread 17 at entry cutting the radial slot 16, and thence turning its edges apart, such that the thread comes to lie therebetween asin Fig. 1.

It will thus be seen, that the invention rovides an efficient fastening where metal sheets are to be held to other sheet or plate elements of metal or other material, the entire result being effected most simply and directly. And, as seen, special punching tools for forming the radial slot and laying the edges may be used, or more simply yet, particularly where the gauge of the stock is not great, the screw threaded element itself may form its own radial slot and positioned edges.

Other modes of applying the principle of the invention may be employed, changebeing made as regards the details disclosed, provided the means stated in any of the following claims, or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention 1. A sheet metal fastening,comprising a screw-threaded metallic element having a tool-engaging head and having a thread starting at the point with a very'steep pitch,

the pitch decreasing toward the head to provide a spacing between threads equal to sheet metal gauge.

2. A sheet screw-threaded metal element having a square thread starting at its pointwith a sharp cutting edge and very steep pitch, the pitch decreasing toward the head to provide a spacing between threads equal to sheet metal gauge.

Signed by me this 9th day of May, 1928. CHARLES D. CANNON.

metal fastening, comprising a, 

